Tumor growth, spread, and eventual invasion into surrounding tissues and structures in the body continues to be an unresolved disease state, having a profound impact on cancer patient outcomes.
Aggressive therapies are often ineffective at stemming growth of the tumors over the long term, and can often contribute to pain and suffering of treated patients.
Perineural invasion of cancerous tumors is a hallmark of many aggressive forms of cancer. Often, patient outcomes diminish dramatically once perineural invasion has begun. Furthermore, pain and patient discomfort may be associated with such perineural invasion, the direct effects of which can have negative impact on patient outlook, optimism, and outcome. Long term use of analgesic medications to counteract such pain can also have detrimental effects on patient outlook, optimism, and outcome.
There are several approaches available for treating cancer-related pain.
Opioids are often used as full agonists at the morphine receptor (e.g., morphine, oxycodone, hydromorphone), or partial agonist opioids (e.g., buprenorphine). Opioids hyperpolarize nociceptive cell membranes, shorten the duration of their action potentials, and inhibit the release of excitatory mediators. Chronic use can lead to neuropathic pain and generally is accompanied by many side effects.
Anti-inflammatory drugs, non-steroidal anti-inflammatory drugs (NSAIDS) decrease inflammation by inhibiting the synthesis of peripheral prostaglandins. NSAIDS are often effective at treating cancer pain that does not originate from nerve damage.
Neuropathic cancer pain is often treated with anticonvulsants, antidepressants, corticosteroids, capsaicin, opioids, and lidocaine patches.
Radiotherapy, radionuclide therapy, etc. employs ionizing radiation focused at cancer cells. Generally, this approach causes apoptotic death of tumor cells, and radiosensitive inflammatory cells.
Neurolytic celiac plexus block can be effective in the treatment of cancer pain but is accompanied by several risks and complications (including paraplegia). Often the celiac plexus is blocked with a 10% phenol solution or absolute alcohol solution. Celiac block can also lead to hypotension (complication of lumbar sympathetic block complications), or paraplegia due to volume spread of solution into the spinal cord. Thus, existing procedures are fraught with complications.
Intraspinal drug administration is an approach that is used to deliver pain medication directly into the spine, termed ‘spinal analgesic chemotherapy’ and can improve the effect of opioid, NSAIDS, and other drug treatments through localized delivery into the spine.
Bone cancer can be particularly painful. Pain progression of bone cancer pain is usually a dull, constant pain, which gradually increases in intensity over time. As the cancer progresses, a breakthrough or severe pain can emerge spontaneously or with movement or load bearing. Such breakthrough pain is often acute, severe, debilitating, and difficult to control.